Control mechanism for supercharged aircraft engines



Aug. 30, 1949. F. c. MOCK ETAL CONTROL MECHANISM FOR SUPERCHARGEDAIRCRAFT ENGINES Filed Jan. 10, 1944 4 Sheets-Sheet l INVENTORSF/PA/vkcT/Vack JAY A.BOL7' Aug. 30, 1949. F. c. MOCK EIAL 2,480,758

CONTROL MECHANISM FOR SUPERCHARGED AIRCRAFT ENGINES Filed Jan. 10, 19444 Sheets-Sheet 2 E N G'l/VE VE- F o, PROPELLER J72 ENG/IVE GUVEk/WK R Mq mmvrons FRANK C. 1706K BY JAVA. BOLT 1949- F. c. MOCK ET AL 2,430,758

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CONTROL MECHANISM FOR SUPERCHARGED AIRCRAFT ENGINES Filed Jan. 10,.19444 Sheets-Sheet 4 73 Press. fiss- 5w.

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w 2c POWER LEVER P05lTl0N FRANK/ZZWJE E F E yAYAaoLT Patented Aug. 30,1949 CONTROL MECHANISM you surna- CHARGED Amcimr'r ENGINES A. Bolt,South Bend, Ind., assignors to Bendix Aviation Corporation, South Bend,Ind., a corporation of Delaware Application January 10, 1944, Serial No.517,622

35 Claims. (CI. 6013) Frank 0. Mock and Jay This invention relates tocontrols for aircraft power units utilizing one or more superchargers.or supercharging stages; it is adapted primarily cally or engine-drivensupercharger and a turbo booster or supercharger arranged in seriestherewith and functioning as an auxiliary, and while certain novel andadvantageous results are attained with such arrangement, it will beobvious that our improved control system may be adapted for power unitsemploying turbo supercharging exclusively, or a combination ofmechanical and turbo or exhaust-driven or controlled compressors orsuperchargers.

A variable datum type of boost or supercharger control is used, and theboost control datum may be set by means of a power control lever in thepilots compartment, which lever may at the same time set a propellerpitch governor, to thereby correlate the engine speed with the chargingpressure and prevent both the charging pressure and the developedhorsepower from exceeding permissible or safe values.

The engine-driven supercharger applies the required charging pressure tothe intake manifold posterior to the throttle while the turbosupercharger applies a coordinated carburetor inlet pressure to theinduction passage anterior to the throttle. The variable datum controlincludes a device such as a bellows or aneroid influenced by manifoldpressure and another bellows or aneroid under the inflence of carburetorinlet pressure, said aneroids being provided with datum springs variablyloaded by cams mounted on a shaft controlled by the pilot's controllever. One of these cams sets the intake manifold pressure datum whichis automatically maintained by a servo-motor controlling the enginethrottle, while the other cam sets the carburetor inlet pressure datumwhich is automatically maintained by an aneroid-controlled switch havingan electrical connection with a reversing motor functioning to variablyposition a waste gate located in the exhaust conduit. Since an exhaustdriven turbo compressor tends generally to balance the intake pressurerise across the turbo driven blower against the exhaust pressure dropacross the turbine blades, any fixed position of the control maintains asubstantially constant carburetor deck absolute pressure via, pressure5g "any desired ratio of intake in the immediate region or thecarburetor inlet, and by properly coordinating the datum cams,

manifold and carburetor deck pressure may be obtained. In one form ofthe invention a speed-control cam is mounted on the same shaft with themanifold-pressure and carburetor inlet pressure datum cam andcoordinated therewith, thereby providing a predetermined schedule ofintake-manifold pressure, carburetor inlet pressure and engine R. P. M.at each setting of the power control lever; while in another form anindependent speed control is provided and carburetor inlet pressurevaries in relation to engine speed with variations in power leversettings.

The term predetermined schedule" as used herein refers to a set ofcorrelated values (which may be established by tests or based on enginecharacteristics) of manifold pressure, engine R. P. M. and carburetorinlet pressure to obtain specified power outputs. As is generally known,a given engine may develop the same power at a given engine R. P. M. andcharging pressure as it does at a higher speed and lower pressure, or ata lower speed and a higher pressure,but the efliciency, engine coolingand other engine characteristics will vary. Thus, for a given engine,particular values of engine speed, chargin pressure, and carburetorinlet pressure are better suited to producing a selected power outputthan are other values. With the proper data in hand as to the relativevalues or manifold pressure, speed and carburetor inlet pressure bestsuited to give any selected power output, the present control mechanismmay be readily set to maintain this relationship or schedule.

Furthermore, a problem presents itself in view of the construction andoperating characteristics of a turbo booster or supercharger. With aturbo booster or supercharger the control is usually initiated throughregulation of the exhaust pressure on the turbo blades, and sinceexhaust pressure is a factor of engine efliciency, it is desirable tohave a control which maintains the most effective charging pressure witha minimum of throttle loss and exhaust restriction. In the presentinstance the mechanical or engine-driven supercharger may be caused toapply the required pressure at the intake manifold up to a certaincritical altitude, during which time the turbo booster may be caused toapply a predetermined auxiliary pressure on the air intake duct leadingto the carburetor, or to remain substantially inactive or at an idlingspeed, and to automatically increase in speed when additionalsupercharging with ancient utilization or exhaust pressure on theturbine driving rotor, the-control being similarly effective when theplane moves from higher to lower altitudes.

The present invention therefore includes among its objects:

To provide an improved control for aircraft power units employing one ormore superchargers or supercharging stages of the turbo type;

To provide an improved supercharger control for internal combustionengines for aircraft having a multi-step supercharging system which willmaintain predetermined chargin pressures at the intake manifold and atthe inlet to the carburetor coordinated to produce the selected poweroutput with a minimum of throttle loss;

To provide a variable datum type of multi-stage supercharger controlparticularly adapted for power units employing mechanical and turbo typesuperchargers in series;

To provide a power control for internal combustion engines of aircraftcapable of automatically n... :itaining a predetermined schedule ofcharging pressure at the intake manifold, pressure at the intake to thecarburetor, or carburetor deck pressure, and engine speed or R. P. M;

To provide an improved control for supercharger systems utilizing amechanically or engine-driven supercharger for the first or initialstage and a turbo-type, supercharger for the succeeding stage or stagesand wherein a variation is required,

in supercharger pressure from a predetermined schedule, resulting forinstance from a change in engine speed, is compensated for by a changein the pressure rise across the turbo;

To provide a control of the type specified wherein the speed of theturbine is under accurate regulation at all times;

To provide a control for turbo superchargers arranged in a manner suchthat the turbine is maintained in a state of rotation during low powerengine operation to thereby promote sensitivity and quick accelerationwith a minimum of power loss in turbo operation;

To provide a convenient and simplified mechanical override forsuperchargers employing a plurality of supercharging steps or stages andparticularly wherein at least one is of the turbo type;

To provide an improved electrical control for multistep superchargers;

And to generally improve and render more flexible and sensitive inoperation supercharging controls for aircraft.

Many other objects and advantages will be readily apparent to oneskilled in the art from the following description taken in connectionwith the appended drawings, in which:

Figure 1 is a diagrammatic sectional view of a control unit inaccordance with the invention;

Figure 2 is a schematic diagram including the electric circuits andccactlng switch mechanism of the control unit;

Figm-es 3 and 4, are curve charts illustrative of performancecharacteristics obtainable by the control unit of Figures 1 and 2;

Figure 5 is a view similar to Figure iication; and

Figure 6 is a curve chart illustrative of performance characteristicsobtainable by the unit of Figure 5.

with particular reference to Figure 1, there is shown an inductionconduit It for an internal combustion engine having an air inlet or so 1of a modi- 00p ,asection izleadingtoamainventm'i i3 and 75 a boostventuri l4, and a section it leading to the entrance of a superchargerit having an annular discharge ring I! adapted to deliver air underpressure. to intake manifold II which supplies the respective cylindersof the en ine. The supercharger It as herein illustrated is of themechanical driven type, the drive being taken from the engine crankshaft, cam shaft, or other rotating part and transmitted to thesupercharger rotor through suitable gearing, indicated at Ilia, Fig. 2.The supercharger as here shown is of the single speed type, but couldobviously be of the multi-speed or multi-stage type. Fuel may besupplied to the engine by any desired fuel-feeding system,,such as acarburetor I9 of the pressure feed type, an example of which isdisclosed in Patent No. 2,361,227, issued to Frank C. Mock October 24,1944, which carburetor receives fuel through pipe 20 and discharges itthrough nozzle 2|.

A throttle 22 variably limits the quantity of air flowing through theinduction passage to the cylinders of the engine and is controlledthrough lever 23 and link 24 by mechanism hereinafter described.

A propeller pitch governor, indicated generally at 24a, controls thepitch of the propeller blades, not shown, to thereby maintain the enginespeed at a value determined by the position of lever 25 controlledthrough link 2G by mechanism to be described. The propeller pitchcontrol may be of either the electric, hydraulic or other known type.

A turbo-type supercharger is generally indicated at 21 and includes animpeller casing 28 adapted to discharge into the induction conduit l0and having an impeller 29 therein, the said impeller being secured on ashaft 30 which projects through a rotor casing 3! having a turbine orrotor 32 therein also secured on said shaft, the casing 3| constitutingan extension of exhaust conduit 33 and being arranged to receive theexhaust discharge in whole orxin part. The speed of rotation of therotor 32 is determined by the position of a waste or blast gate 34rotatably mounted in an extension 35 of the exhaust conduit 33 andprovided with a lever 36 connected by means of link 31 with arm 38driven from the armature shaft 39 (see Figure 2) of a motor 40, thelatter being of the reversing type and provided with field coils 4| and42 arranged in opposed relation so that when current is directed throughcoil 4] the armature rotates in a direction to close the waste gate 34and when directed through coil 42 it rotates in the opposite directionto open the waste gate.

To prevent overrunning of the motor, limit switches L 1? may be locatedfor contact by the arm 38, said switches being illustrateddiagrammatically in Figure 2. Other equipment includes a pair of relaysR R the latter being provided to avoid passing the motor current throughthe contact circuit and consequent heavy arcing across the points.Relays R R are provided with the usual solenoids and fixed contacts Ma,4211 and movable contacts 4"; and 42b.

Means in the form of a power control unit is provided whereby the pilot,through a single lever 58, is enabled to have direct mechanical controlof the supercharging pressure and propeller speed governor over acertain range of throttle actuation, whereupon the control becomesautomatic. This power control unit has certain features in common withthe control units illustrated in the copending applications of Frank C.

Mock, Serial No. 440,669 filed April 27, 1942, now

Patent No. 2,453,851, and Serial No. 443,042 filed May 15, 1942, as willbe rendered apparent from a comparison of the respective structures.Briefly, it' comprises a casing 43 having a mam shaft 44 rotatablymounted therein. A lever 45 is secured to the shaft exteriorly of thecasing and is pivotally connected to link 24 operatively c nnected tothe en ine throttle. A second lever 6 having a spur gear or pinion 47rotatabl moun ed thereon is also secured to shaft 44, whereby rotationof lever 48 rotates lever 45 and variably positions the throttle 22. Amember 48, somewhat resembling a. quadrant, is provided and has aninternally-toothed segment or gear portion 48a in mesh with pinion 41,said member 48 being loosely mounted or otherwies supported for rotationon shaft 44'. A gear 49 is also rotatably mounted on shaft 44 and hasone segment in constant mesh with pinion 4'! and another segment inconstant mesh with a gear rack 58 forming a connection between twoservo-motor pis-. tons and 52 slidably received in cylinders 54 and 53and provided with small oil by-pass ports 55 and 56. A spring 51 urgesthe pistons to the left, corresponding to closed throttle position. Thegears 41, 48 and 49 form a planetary spur gear train whereincounterclockwise movement of either or both gears 48 and 4'9 rotateslever 46, shaft 44 and lever 45 in a counterclockwise direction, andopens the throttle 22, and clockwise movement of said gears closes thethrottle.

For controlling the power output of the engine, a control lever 58 .ispivotally mounted in the pilots compartment and is connected by link 59with an arm 68 on the member 48, whereby the pilot is enabled todirectly control the position of said latter member. The member 48 isprovided with cams or cam surfaces 8|, 62 and 63 adapted respectively,to vary and correlate engine speed, datum of the first superchargingstep initiated through supercharger I6, and datum of the second step orauxiliary supercharger through turbo supercharger or booster 21. Cam 6|is engaged by roller or other type of follower on an arm of a pivotedlever 84, the other arm of which is connected by link 26 to arm 25 ofthe propeller pitch governor 2411; cam 82 is engaged by a roller orother type of follower on an arm 65 of a pivoted bell crank, the otherarm 66 of which is provided with fingers 6'l straddling a cylindricalguide 68 of a datum rod 69 and engaging a spring collar I8 slidablymounted on guide 68 for variably loading a boost control datum springII; and cam 63 is engaged by a roller or the like on the one end of apivoted lever I2 having fingers 13 for variably loading the datum springassembly of a turbo supercharge or boost control unit, to be described.

A sealed corrugated bellows l4,which may be partially evacuated ifdesired, is adjustably mounted at its left end in the wall of a chamber15 and has its free end secured through a universal connection 16 to theleft end of datum rod 69. The datum spring 'lI prevents the bellows 14'from collapsing by reacting against spring retainer 11 threadedlyreceived on rod 69 and locked in its adjusted position by a conventionallock nut or the like. The bellows I4 is subjected to engine char ingpressure by means of a pressure-transmitting pipe or conduit I8connecting chamber I5 to intake manifold I8 Movement of rod 89 istransmitted through a pivoted lever I9 to a servo-motor control valve orvalve member 88 provided with lands 8|, 82,

' spring and each having I I5 slidable 83 and grooves 84 and 85. Thevalve is slidably received in a cylinder having grooves 88, 81, 88, 89and 98. The land 82 is somewhat narrower than groove 88, and in itsneutral position is substantially centrally located relative to saidgroove; the lands 8| and 83 at such time just, or very nearly, sealgrooves 88 and 98.

A pump 9|, which may be either the main oil pump for the engine or apump for an auxiliary hydraulic system, supplies oil through pipe orconduit 82 to the groove 88 of the servo-valve cylinder, and ducts 93and 94 lead from the grooves 89 and 81 to the left and right-handchambers 53 and 54 respective] of the servomotor. A drain duct 95connects grooves 86 and 98 with the interior of casing 43 and a pipe orconduit 98 returns drain oil from the casing to pump 9|.

In order to limit the supply of high pressure oil to cylinder 53 at suchtimes as the throttle is wide open with the pistons 5| and 52 in anintermediate position, a servo-motor tripping device is provided andcomprises a slidable stop 9'! urged to the right by spring 98 and havinga flange 99 adapted to be engaged by cam portion I88 of lever 46 as thelatter approaches within a few degrees of its wide open throttleposition. Movement of stop 9'I-upon further movement of lever 46 movesrod 69 to the left and valve 88 to the right, to thereby increasinglyrestrict and finally cut off communication through servo-valve 88'between oil suppl passage 92 and duct 93 leading to servo-motor chamber53.

In order to prevent hunting of the bellows actuated servo-valve 88, .apair of oppositely disposed cylinders I 8|, I82 are provided and havedamping pistons I83, I84 slidably received therein, each piston beingurged inwardly by a light an extension adapted to closely approach theball-shaped end of an arm I88 of servo-valve 88 when the latter is inits central position. Said cylinders are connected to the interior ofcasing 43 through restricted passages I8I', I82 which limit the rate ofinward travel of the pistons I83, I84. If the valve tends to hunt, armI86 will successively engage the extensions of the pistons to therebyresist movement of the valve to the left or right of its equilibriumposition. Since it is desirable to have the servo-valve 88 respondquickly to any change in the load on spring II, a pair of cylinders I81,I88 are provided in fluid communication with cylinders I 8|, I82 andhave pistons I89, II8 slidably received therein, said latter pistonshaving extensions securedto the end III of arm 88 so as to be actuatedthereby. Upon movement'of arm 66, pistons I89, II8 displace oil incylinders I 8|, I82 and temporarily withdraw which ever of pistons I83,I84 would otherwise interfere with the desired rapid movement of valve88.

For a more detailed description-of the foregoing construction, referencemay be had to Patent No. 2,453,651, heretofore noted.

For controlling the operation of the turbobooster 21 and hence the inletpressure to the carburetor in section I2 of induction conduit I8, thereis provided a bellows or aneroid II2, preferably at least partiallyevacuated, which is adjustably mounted at one end in a chamber II 3connected to the-air intake section I2 anterior of the carburetor bymeans of pressure-transmitting pipe H4. The free or movable end ofbellows H2 is connected to the one end of a rod in guide sleeve H6 andhaving a 76 spring retainer III adjustably secured thereon mam beyondsleeve III; and is provided with a switch -arm I20 carrying a pair ofcontacts I2I, I22

adapted to be moved into alternate engagement with adjacent contactsI23, I24, depending upon the direction of travel of rod II. The contactsI2I, I22, I23 and I24 are electrically connected to the waste or exhaustgate motor 43 through pressure reserve switch HI and turbo speed govemorI31 in a manner which will now be described.

.By referring to Figure 2, it will be noted that a source of electricpower such as a battery B of suitable potential is provided, and has thepositive terminal thereof connected by wires I25, I230 with the positivebrush of the waste gate motor 40 through speed adjusting rheostat I251),the other terminal of the battery being connected by wire I250 with thefixed contacts of relays R R The positive terminal of the battery isalso connected by wires I26o, I21, I2Ia to and through overspeedgovernor contacts (to be described) and thence by wire I2'Ib to contactI22. A branch I21c of wire I21 leads to a contact I23 adapted to coactwith one or the other of contacts I29 and I30 forming part of a pressurereserve switch I3I, functioning to maintain a minimum turbo boost, or toat least maintain the turbo in idling operation during periods when theturbo boost is not required. In the example herein illustrated, pressurereserve switch III comprises a bellows I3Ia responsive to variations inpressure and mounted in chamber Iflb suitably vented to the atmosphere.A spring I3lc or predetermined capacity normally urges the bellowstoward collapsed position. A switch rod I32 is secured to one end of thebellows for movement therewith and carries contact I28. The bellows isin pressure communication with the section I2 of the intake conduit I bymeans oi pipe I33. This pressure reserve switch operates in response toa difierential between atmospheric pressure and the pressure maintainedat the inlet to the carburetor, or carburetor deck pressure in a mannerwhich will be more fully hereinafter described.

Contact I23 connectsby wires I34, I341: and I34b with the solenoid coilof relay RF through limit switch L and contact I24 connects by wiresI35, I35a and I35b with solenoid coil of relay BF through limit switchLP. Contact I2I connects by wire I35 with contact I30 of the pressurereserve switch I3I and thence through contact I23 (when the latter is inengagement with contact I30) wires I2'Ic, I21 and wlrelfla with thebattery. It will be seen that when pressure reserve switch contacts I28and I30 are separated, the circuit is broken between the battery andcontact I2I and the aneroid I I2 can no longer act to open the wastegate 34; and when contact I engages I29, a circuit is closed between thebattery and relay B. through wire I26a, I21, I2'Ie, I29a, I35a, limitswitch I. and wire Ilib, whereupon contacts 4Ia, 4Ib close, therebyclosing the motor circuit to coil H and the waste gate will move towardclosed position. Normally contacts I28 and I are in engagemmt,separation occurring only in the event the pressure differential acrossbellows I3Ia drops to a predetermined value. The manner in which switchIll operates will be more fully described in connection with the generaloperation of the control.

To limit the turbo to a safe maximum speed, an overspeed governor,generally indicated at I31, is provided and comprises conventionalpivoted weights carried by a support I3'Ia which in turn is secured onthe turbo shaft 30. The governor weights act through centrifugal forceto reciprocate a switch rod or like member I33 provided with contact I33adapted to enga e contact I when the turbo speed is below its maximumsafe permissible value and to engage contact I40 when the turbo speedexceeds themaximum permissible value. when contact I39 is in engagementwith I, current may flow from the battery through wires I2Iia, I21,I21a, contacts I33, I, and wire I21b to contact I22. If contact I22 isin engagement with contact I24, the current may then flow through wiresI35, I350 and Ib to relay R of reversing coil H to further close thewaste gate 34, thus permitting control through,

aneroid switch II2; but should a predetermined maximum speed beattained, this circuit will be interrupted by the governor switch I31and a circuit set up from the battery through wires I250, I21, I21a,contacts I39, I40 and wires I42, I34?) with the solenoid coil of relayR, energizing the solenoid of the latter and closing contacts 42a, 42b,thereby closing the motor circuit to reversing coil 42 and opening thewaste gate until safe speed is resumed.

'There may be instances when the pilot will desire engine speed inexcess of that scheduled, as for example during cruising where anincreased speed ratio with respect to manifold pressure and carburetorinlet pressure would result in more economical operation, or to obtain alow-pitch setting for ground travel, take off and landing. Accordingly,a convenient propeller override is provided consisting of a lever I46which may be mounted in the pilot's compartment and connects by link I41with lever 64, the latter being normally urged into contact with cam GIby means of spring I48. In Figure 1, link I41 connects with lever 64through lost-motion connection I41a, which permits the lever 64 freetravel during automatic operation through the cam 6|, but in the eventit is desired to override the cam, lever I46 may be urged to the left,whereupon the cam follower carried by lever 64 may be advanced beyondthe range of the cam GI. The lever 64, unless held in the overrideposition, will automatically move back to normal automatic operation dueto the action of spring I48. In Figure 2, the

lever 04 is of bell-crank shape and is indicated.

at 64', and the link I41 connects therewith through the medium ofoverride lever I41, which compares with the lost-motion connectionflflaof Figure 1. The same results are obtained in this instance as in Figure1.

In describing the operation of the control mechanism, any practicalschedule of manifold pressure, carburetor inlet pressure and R. P. M.may be assumed, it being obvious that such schedules are governed by thecharacteristics of diiferent types or makes of engines, and once themost eflicient or effective schedule has been established by tests orotherwise, the datum cams and coacting parts may be set accordingly.

15 At sea level with the throttle closed and the engine idling, thepilot's-control lever 58 will be in the extreme left-hand position andthe cam followers of levers 65, 12 and 64 will be in engagement with thelow portions of their respective cams, datum springs II and 8, beingloaded but with moderate forces which are insufiicient to preventpartial collapse of the bellows coacting therewith. Due to the collapsedstate of bellows 14, the valve 80 is in its extreme right-hand position,whereby oil under pressure is transmitted from pipe 92 through the servovalve and passage 94 to the chamber 54, where it acts on piston andtogether with the spring 51 holds the rack 50 in its extreme left-handposition, thus substantially locking the gear 49.

As lever 58 is gradually moved to the right, quadrant 48 will move in acounterclockwise direction, causing the pinion 41 to move in a similardirection around the gear 49, this movement of the pinion beingtransmitted through lever 46, shaft 44 and lever 45 to the throttle link24, thereby opening the throttle. As the throttle opens the chargingpressure acting on bellows 14 increases and tends to maintain thebellows in its collapsed state, but as lever 58 is moved further,therise in cam 62 approaches and engages the follower of lever 55,thereby moving the fingers 61 to the right and increasing the load onspring 1| tending to expand bellows 14. The rise in cam 62 increases thespring load at a rate greater than the rate of increase of thepressure-collapsing force resulting from" the manual opening of thethrottle, whereby the spring force overcomes the pressure force andmoves the rod 69 to the right and through lever 19 moves the servo-valve80 to the left until the valve reaches its normal equilibrium positionin which the land 82 is substantially centered relative to the groove88. At this time the throttle is partially open and the ma chine isoperating at a speed above normal idling but preferably less than theminimum values experienced during cruising. Through this range ofmovement of throttle lever 58, the pilot has a direct mechanical controlover the throttle, the boost control being substantially inoperativealthough the turbo is rotating at a predetermined speed due to theaction of the pressure reserve switch l3l. This initial manuallycontrolled throttle range is desirable since the engine manifoldpressure at idling and near idling tends to be unstable and will resultin hunting action of the boost control.

If lever 58 is now moved an additional amount beyond the range of directthrottle actuation, cam 62 through bell crank levers 65 and 66 andfingers 61 further load the spring H and move the rod 69 to the rightand the servo-valve 90 to the left from the neutral or equilibriumposition. Oil from pipe 92 is then transmitted through the servo-valve80 and passage 93; and the chamber 54 is connected through the passage94 and valve 90 to the passage 95 for returning oil to the casing 43.The high pressure oil forces piston 52 and rack 50 to the right againstspring 51, thereby rotating gear 49 in a counterclockwise direction,causing pinion 41, lever 46, shaft 44 and lever 45 to also move in acounterclockwise direction, thereby opening the throttle 22 until theengine manifold pressure transmitted to the chamber 15 becomessufliciently great to collapse the bellows l4 and move the servo-valve80 toward its equilibrium position.

During operation above the direct manually controlled throttle range,the pilot, in positioning lever 58 and quadrant 48 with its cam 62determines the load on spring 'II and therefore determines the pressurein chamber 15 which the con trol will automatically maintain, if at agiven setting of the lever 59, the charging pressure decreases as by anincrease in altitude, bellows 14 will expand slightly, causing th evalve to move to the left and increase the flow of oil to the servochamber 53, thereby moving the piston 52 further to the right andopening the throttle an additional amount so as to maintain the relativecharging operating pressure, An i crease in charging pressure as by adecrease in altitude will produce the reverse effect and will cause aslight closing of the throttle.

The pilots control or throttle lever 58, in positioning the throttle 22,also determines the carburetor'inlet pressure setting by means of cam63, and the propeller pitch governor setting by means of cam 6|.

Normally, the engine-driven supercharger It has more than sufilcientcapacity to maintain the charging pressure selected by lever 58 fromground level up to some predetermined or critical altitude, theparticular altitude being dependent upon the value of the pressureselected. For example, if at ground level lever 59 is placed in its midposition, the charging pressure determined by cam will obtain in theengine manifold [8 with the throttle only partially open. If the planenow ascends, the boost control will gradually open the throttle tomaintain the selected charging pressure notwithstanding the reducedatmospheric pressure; and this will continue until an altitude isattained at which the throttle is substantially wide open, or thecritical altitude for the blower is attained.

Up until the time the critical altitude for the first charging step isapproached or reached, the pressure applied to aneroid chamber 3 fromsection l2 of the intake duct I. may be suflicient to maintain bellows II2 in a collapsed state, or it may drop to a point where the bellowswill be extended by datum spring Ill, depending upon the schedule ofcarburetor inlet pressure to be maintained with respect to intakemanifold pressure. If there is no turbo or auxiliary charging pressureand if frictional losses are neglected, carburetor deck pressure wouldsubstantially equal atmospheric pressure, which would ordinarily beabove scheduled carburetor inlet pressure. Under such conditions, theaneroid 2 would remain in a collapsed condition up to a certain altitudeand the turbo would simply rotate'at idling speed, due to the action ofthe limit switch I3l. Such altitude may vary over a wide range,depending upon scheduled carburetor inlet or deck pressure, or there maybe instances when the pressure at this point will drop to that scheduledirrespective of altitude. Preferably the datum cams and springs shouldbe given a setting such as to produce a minimum of time lag when turboboost is required. However, since the intake manifold pressure iscontrolled quickly and independently of the turbo control by thecarburetor throttle and air intake datum control, the exhaust controlmay have a certain amount of time lag without materially affecting poweroutput of the engme.

When the pressure in the intake section l2 of the air intake conduit [0drops to a predetermined value, or to a point where it no longermaintains the bellows H2 in a collapsed state, switch rod H5 moves tothe right, thereby bringing contact I22 into engagement with contactI24, closing the circuit from the battery to the solenoid coil of Forexample.

"chamber I4 at the selected value.

relay B through wires I240, I21, I2Ia, overspeed governor. contacts I29,"I, wire I2lb, contacts I22, I24. wires Ill, Illa, limit switch 1.. andwire Ilib; energization of the solenoid of relay R causing contact 4Ibto engage contact 4 la, whereupon a. circuit is closed from the batterythrough wire I29, rheostat I2lb. wire I2ia, through the motor and coil4|, relay contacts 4Ib, 4 la and back to the battery through wire I2lc;to thereby move waste gate 94 toward closed position and accelerate theturbo to a speed where it will supply the required schedule of pressurein coniunction with the supercharger II.

As the charging pressure at the intake manifold becomes effective, thepressure in chamber will tend to rise above the value selected by datumspring II; however, the bellows l4 and servo-valve function aspreviously described and partially close the throttle to maintain thepressure in Upon further increase in altitude the boost controlgradually opens the throttle and/or closes the turbo waste gate, andmaintains the scheduled pressure up to a point where the capacity or theturbo is reached. If desired, an additional charging step or steps couldbe provided to increase the capacity of the system.

Should the pressure in intake section I2 rise above the scheduled valueas determined by the setting of spring H9, bellows H2 collapses and rodI It moves to the left, thereby closing contacts I2I, I29, whereuponcurrent flows from the battery through wires I2, I21, I210, pressurereserve switch contacts I 24, I29, wire I39. contacts I2I, I23, wiresI34, I34a, limit switch L wire I24b to solenoid coil of relay RP,causing contact 42b to engage contact 424, closing the motor circuitfrom the battery through wire l2l, rheostat I25b, wire I2Ia, through themotor and coil 42, contacts 421), 42a and back to the battery throughwire I25c; causing motor 44 to reverse the drive on waste gate 34 andmove the latter toward open position, thereby reducing the speed of theturbo.

The pressure reserve switch III functions to maintain a minimum turboboost to insure that the turbo will continue to operate at moderatespeeds even during idling or low power operation of the engine, tothereby improve acceleration and avoid power loss in overcoming inertiawhen turbo charging is demanded. This device maintains a minimum turbopressure rise of, for example, 1" of mercury across the turbo drivingrotor 22 by regulating the position of the waste gate 34 in a mannersuch that the required amount or exhaust pressure will be applied tokeep the rotor operating at moderate speeds even though the engine isidling or operating at low power at which time the exhaust pressure isat a minimum, the carburetor deck pressure is above that scheduled, and.the switch I29 is in a position which tends to maintain the waste gateopen, viz., to the left with contacts I2I and I2! closed.

By way of example, let it be assumed that the pressure of the atmospherein which the plane is moving at any one moment is 29.5" Hg,corresponding substantially to ground level operation; and let itrurther be assumed that the power control lever II is set for a moderatepower output. Since the engine-driven supercharger It has sufflcientcapacity to maintain such selected power up to a predetermined altitude,there is no need for turbo supercharging until this altitude isapproached, and consequently the turbo datum the circuit throughcontacts I22, I24 to accom-- plish closing of the waste gate 24 only asthis altitude is approached or exceeded. Below this altitude, however,the increased pressure on bellows II2 would collapse the bellow andclose the switch. contacts I2l, I23 establishing a circuit as heretoforepointed out which would energize armature winding 42 and tend to fullyopen the waste gate. Were it n t for the pressure reserve switch, theturbo would robably stop or slow up to a very low speed since theexhaust pressure effective on the turbo with the waste gate open wouldbe insuflicient to maintain the turbo operating at moderate speeds as isdesired for rapid resumption of turbo charging upon subsequent rapidincrease in altitude or sudden demand for increased power output.

In the event the turbo speed tends to decrease below the desired minimumvalue the decreased pressure in conduit I2 transmitted through pipe I42to bellows Illa. becomes insuillcient to overcome spring I3lc and thebellows will collapse breaking the connection between contacts I28, I34and interrupting the circuit through contacts I2I, I29 to armaturewinding or coil 42, thereby preventing iurther opening or waste gate 34and further reduction in turbo speed. Further decrease in thediflerential pressure across the turbo results in further collapse ofbellows I3Ia and a closing or contacts I28, I29 whereby a direct circuitis established from the battery through wires I26a, I21, I210, contactsI28, I29. wires I290, i351: limit switch L, wire I351) to solenoid coilof relay R causing contact III!) to engage 4Ia. and closing the motorcircuit from the battery through the motor and coil H, whereupon themotor moves the waste gate 34 toward closed position and increases thespeed of the turbo to reestablish the minimum turbo boost pressure asdetermined by spring ISIc. As soon as the minimum diflerential pressureis established the bellows IlIa expands and breaks the circuit throughcontacts I29, I29 to stop further closing of the waste gate. Thusreserve switch I3I functions to control the waste gate to maintain atall times a minimum turbo boost and consequently a minimum turbo speed.

The turbo overspeed governor functions to maintain the turbo speedwithin safe limits. Thus should the turbo exceed a certain maximum, thegovernor operates to close contacts I39 and I49, whereupon currentpasses from the bat tery through wires I26a, I21, I2Ia, contacts I39,I40, wire I42, limit switch L to wire I 24b through solenoid coil ofrelay R, causing contact 42b to engage contact 42a, thereby closing themotor circuit through coil 42 and reducing the turbo speed to themaximum determined by the setting oi! the overspeed governor.

The chart of Figure 3 plots carburetor inlet pressure against altitudeat some constant manifold pressure and R. P. M. It will be noted that atsea level up to a certain altitude, the turbo boost closely followsatmospheric pressure, and when an altitude is reached where the requiredcarburetor inlet pressure would otherwise drop below that scheduled, theturbo acts to maintain the required pressure. The curved line whichfollows the line denoting atmospheric pressure indicates the minimumboost pressure maintained by the pressure reserve switch. Theoretically,with a constant manifold pressure and engine speed, the carburetor inletpressure follows a substantially straight line until the criticalaltitude for both superchargers is attained; whereas actually this linemay simulate to some extent a sine wave due to the fact that it would bediflicult to maintain the turbo boost at a fixed value.

Figure 4 is a curve chart illustrating a schedule of R. P. M., manifoldpressure, carburetor inlet pressure and pressure between the throttleand engine-driven supercharger vs. power. ter might also be calibratedin degrees of control lever setting. The full lines indicate thescheduled engine speed, manifold pressure and carburetor inlet pressure,while the dotted lines indicate what is actually obtained. Thus atidling, the manifold pressure and carburetor inlet pressure are somewhatgreater than that scheduled, while the R. P. M. is less than thatscheduled. This is due to the fact that the engine has not yet warmed upor reached a degree of operation which will bring the respectivepressures up to those scheduled. As the throttle is opened, manifoldpressure rises and is followed by carburetor inlet pressure, the latterbeing maintained slightly above that existing between t e throttle andengine-driven supercharger, so that ample The latpressure is availableat the throttle without waste,

or without utilizing power in needlessly driving the turbo.

The anerold H2 is preferably connected into the induction conduit orpassage adjacent to or in the region of the carburetor deck. Thisconnection has certain important advantages; for instance, should therebe duct losses or leaks between the turbo and the carburetor, either ofan inherent nature or such as might result from enemy gun me or othercauses, the carburetor would continue to be supplied with the correctamount of air as long as the turbo capacity is not exceeded; anddifferent installations with different duct losses may be controlled byidentically calibrated control units.

It is to be understood, however, that the aneroid II2 may be influencedby pressures from any source which are representative of or functionas areference with respect to pressures prevailing in the region of thecarburetor deck or in the induction passage between the turbosupercharger and the carburetor.

It will be seen that for each scheduled manifold pressure and R. P. M.,a fixed value of carburetor inlet pressure and manifold pressure rise iscalled for by the datum controls, and if these are not obtained, therespective factors will become unbalanced and the turbo waste gate willbe accelerated or retarded to establish equilibrium. To prevent huntingofthe electrical controls, the contacts should be separated suchdistances as will permit some pressure change without changing the wastegate position. The result will be that the control of carburetor inletpressure will not follow an exact straight line. Close manifold pressurecontrol may be obtained by some throttling at the carburetor, which isacceptable since it tends toward a more stablecontrol. This throttlingwill not occur above the critical altitude of the engine-drivensupercharger, since under this condition both the manifold pressure andcarburetor inlet pressure will be lower than the control will call for,and therefore the throttle will be wide open and the turbo willoverspeed unless controlled by the overspeed governor.

Figure 5 illustrates a turbo control unit of modified construction witirespect to that shown in Figures 1 and 2, wher in the engine speed maybe varied independently of the power control lever setting and whereinthe carburetor inlet pressure maintained by the turbo superchargerdepends not only upon the setting of the power controllever, as in thedevice of Figure 1, but also upon the operating speed of the engin InFigure 5, parts which correspond in function to those of Figures 1 and 2are given like reference numerals except that a prime has been added.Intake manifold pressure and posterior throttle pressure, (pressurewhich exists between the throttle and the engine-driven supercharger),are communicated,\respectively, to chambers I50 and I5I defined byhousing I52 partitioned by a diaphragm I53, chamber I50 having pressurecommunication with the intake manifold I8 by means of tube or pipe I54,and chamber I5I having pressure communication with the conduit I0between the throttle 22' and the supercharger I6 by-means of pipe ortube I55. Rod H5 projects through the housing I52 and is secured to thediaphragm I53 and consequently is movable therewith. To ensure againstleakage, sealing diaphragms I55 and I51 are secured at their centers tothe shaft or rod 5' on opposite sides of the main diaphragm I53, thesaid sealing diaphragms being anchored at their outer edges by means ofJournal boxes I58 and I59. The rod II5' carries datum spring II8 whichat one end abuts adjustable collar III' fixed to said rod and at itsopposite end abuts slidable collar 9', the latter being engaged by bellcrank lever I2 acted on by datum cam 63 secured on shaft 44'.

Carburetor inlet pressure is communicated to chamber H3? by means oftube or pipe I33, said chamber having therein bellows II2 which at itsfree or movable end is connected to the left-hand end of rod 5'.

The right-hand end of rod 5' carries switch contacts I2I and I22 adaptedto engage contacts I23 and I20, which contacts correspond to thecontacts I2I, I22, I23 and I20 of Figures 1 and 2, the electricalcircuit associated with these con.- tacts being the same as thatheretofore described and operating in the same manner. Thus when the rod5' moves to the right and contact I22 engages contact I24, the wastegate is moved towards closed position -to thereby increase the speed ofthe turbo, and when said rod moves to the left and contact I2I' engagesI23, the waste gate is moved towards open position and the turbo speeddecreased.

The propeller pitch governor 24a is provided with a separate manualcontrol by means of lever I80 and connecting link I6I;' while the datumcam 63 on shaft 44 together with datum cam 62' act automatically tomaintain correlated manifold pressure and carburetfir inlet pressure inaccordance with the setting of power-control lever 50'.

In operation, the pressures communicated to the chambers I50 and I5I areindicative of those existing in the intake manifold I8 and in theconduit 40 between the throttle and the supercharger, the latterpressure being termed posterior throttle pressure. Sinceintake manifoldpressure is normally higher than that between the throttle and thesupercharger IS, the tendency will be for the diaphragm I53 to urge therod II! to the left, which movement is opposed by the datum spring 8';and likewise carburetor inlet pressure in chamber I I3 normally urgesthe bellows I I2? towards collapsed position against the resistance ofdatum spring 8'. The force of datum spring 0' as variably determined bythe setting of 'the power control lever 58', and

cam 53 is balanced against the sum of the forces obtained fromcarburetor inlet pressure acting and consequently the superchargerpressure rise is varied at any scheduled manifold pressure.

As an aid to a clear understanding of the examples of operation whichfollow, it may be noted that the absolute manifold pressure as detervmined by the setting of cam 62' is equal to the absolute atmosphericpressure plus the rise in pressure through the turbo-supercharger minusthe pressure drop or throttling loss across the carburetor, plus therise in pressure across the engine-driven supercharger; and obviouslyany drop in the engine-driven supercharger pressure rise as results withdecrease in speed must be compensated for by an increase in theturbo-supercharger pressure rise, or by a decrease in the throttlingloss of the carburetor if the scheduled manifold pressure is to bemaintained.

Assume now, for example, that an airplane equipped with the control isoperating at an altitude which calls for turbooperation to maintain thescheduled carburetor inlet pressure, and the pilot decreases the speedfor economical cruising operation while maintaining the scheduledmanifold pressure as determined by cam 62'. This may be done by theindependent control afforded by lever I60, but a decrease in the enginespeed results in a decrease in the engine-driven supercharger pressurerise and will necessitate either a decrease in throttling loss as byfurther opening of the throttle or an increase in the pressure risethrough the turbo supercharger if the scheduled manifold pressure is tobe maintained. Accomplishing this merely by opening the throttle isdisadvantageous for the reason that the throttle would soon reach wideopen position thus using up the latter portion of the throttle openingrange which preferably should be reserved to the pilot for rapidacceleration if desired and found necessary. Also, in view of thesomewhat unsteady operation of a turbo-supercharger, it is desirable toreserve the latter portion of the, throttle opening range so that theboost control may function to variably position the throttle so as tomaintain a constant manifold pressure even though the turbo surges orotherwise varies in operation. These difliculties are avoided by thedevice of Figure wherein a decreasein engine supercharger pressure riseaccompanying a decrease in engine speed results in a drop in thepressure differential across diaphragm I53. This effects movement of rod5' to the right closing contacts I22 and I24 and closing the blast gate,

which in turn increases the speed of the turbo until the increase incarburetor inlet pressure acting on bellows I I2 compensates for theloss in force on diaphragm I53 and moves the rod 5' back to itsequilibrium position. The increase in pressure rise across the turbosupercharger thus at least partially compensates for the decrease inpressure rise through the engine supercharger and makes it possible tomaintain the scheduled manifold pressure.

Preferably the effective area of diaphragm I53 (as reduced by the areaof one or the other of sealing diaphragms I55, I51) is equal to that ofthe bellows 2' so that a decrease in the engine supercharger pressurerise acting on diaphragm I53 will produce an equal increase in pressurein the carburetor inlet acting on bellows H2 and consequently an equalturbo-supercharger pressure rise which will fully compensate for thedecreased pressure rise across the engine-driven supercharger, wherebythe throttling loss reserved for the purposes above discussed willremain constant with variation in engine speed at a' scheduled manifoldpressure. By making diaphragm I53 larger in area than bellows H2, agiven drop in pressure rise across the enginedriven supercharger willproduce a greater increase in the pressure rise across the turbosupercharger and consequently the throttling loss will have to beincreased (by closing the throttle) to maintain the selected manifoldpressure. Likewise if diaphragm I53 were smaller in area than bellowsH2, a given drop in the pressure rise across the engine-drivensupercharger would result in a smaller increase in pressure rise acrossthe turbo-supercharger and consequently the throttling loss would haveto be decreased (by opening the throttle) in order that the scheduledmanifold pressure be maintained.

It will thus be seen that by making the effective area of diaphragm I53larger, equal to or smaller than that of bellows 2', the control willproduce an increasing, constant, 01' decreasing throttling lossrespectively at any scheduled manifold pressure upon decrease in enginespeed and a decreasing, constant, or increasing throttle lossrespectively upon increase in speed.

Let it now be assumed that the pilot is operating at some given or fixedpower setting, and that he desires to increasehis speed whilemaintaining scheduled intake manifold or charging pressure. Lever I60may then be further actuated in the proper direction (as shown towardthe left) to obtain the desired speed, whereupon there will be a rise inpressure across the engine-driven supercharger and a corresponding risein difierential across diaphragm I53 which immediately effects movementof rod 5' to the left, closing contacts IZI' and I23 and opening theblast gate which in turn decreases the speed of the turbo. Rise inpressure across the engine-drivensupercharger must be compensated foreither by an increase in throttling loss or by a reduction in the riseacross the turbo supercharger. With the control of Figures 1 and 2 wherecarburetor inlet pressure is maintained at a value as determined bydatum cam 53,-this compensation is accomplished by an increase inthrottling loss; whereas with the control of Figure 5, compensation isobtained by a decrease in the pressure rise across the turbosupercharger, it being noted however that in the event the rise acrossthe turbo supercharger is reduced to the minimum permitted by pressurereserve switch I3I (Figure 1) without full compensation for theincreased rise across the engine-driven supercharger, such deficiency incompensation will be made up by an increase in throttling loss.

Figure 6 illustrates by means of curves how the carburetor inletpressure varies in relation to engine speed with variations in powerlever settings.

The foregoing specific examples of operation should not be construed asencompassing the entire field of advantages of which the control unit iscapable, nor should they be considered the more important advantages,since various types of power units and operating conditions continuallypresent a multiplicity of problems which the improved control unit maysolve or assist in solving. v

The control unit of Figure 5 may also be arranged for schedulingcarburetor inlet pressure,

manifold pressure and engine speed or R. P. M. with a manual overridefor speed, in which event the cam GI and coacting linkage of Figures 1and 2 would be substituted for the full manual speed control lever Hillof Figure 5.

Although the invention has been described with reference to a particularembodiment, it will be understood that changes in design and arrangementof parts may be adopted without departing from the spirit and scope ofthe invention as defined by the appended claims.

We claim:

1. Control mechanism for an aircraft engine having an air inductionpassage provided with a carburetor having a throttle-controlled airinlet and a supercharging system including a primary supercharger and anauxiliary turbo supercharger in series therewith and powered by anexhaustdriven turbine; said mechanism comprising variable datum controlmeans for said superchargers including an element responsive topressures in said passage posterior to the primary supercharger andhaving means coacting therewith operating to automatically regulate thedegree-of charging pressure of the latter and another element responsiveto pressures representative of induction pressures in said inductionpassage between said turbo supercharger and said throttle and havingmeans coacting therewith operating to automatically regulate the exhaustpressure utilized in driving said turbine, a device adjustable to varythe speed of the engine independently of the throttle, and means havingan operative connection with said variable datum controls and saiddevice whereby said controls and device may be set to maintain apredetermined schedule of manifold pressure, carburetor inlet pressureand engine R. P. M.

2. Control mechanism for an aircraft engine having an intake manifold,an exhaust conduit and an air induction passage provided with acarburetor having a throttle-controlled air inlet and a superchargingsystem including a primary supercharger and an auxiliary turbosupercharger in series therewith and powered by an exhaustdriventurbine; said mechanism comprising a variable datum control for theprimary supercharger including a pressure-responsive element havingpressure communication with said passage posterior to the primarysupercharger and means coacting with said element operating toautomatically regulate the degree of charging pressure applied to saidmanifold, a variable datum control for said turbo-supercharger includinga pressureresponsive element having pressure communication with saidinduction passage between said v having a throttle-controlled inductionpassage turbo supercharger and said throttle and means coacting withsaid latter element operating to automatically regulate the degree ofexhaust pressure utilized in driving said turbine, and means having acommon operative connection with said variable datum controls wherebythe latter may be simultaneously set to automatically maintain apredetermined schedule of manifold pressure and carburetor inletpressure.

3. Control mecha r'iism for an aircraft engine having athrottle-controlled induction passage provided with a carburetor inlet,intake and exhaust manifolds and a supercharging system including aprimary supercharger and an auxiliary turbo supercharger in seriestherewith andpowered by an exhaust-driven turbine; said mechanismcomprising a variable datum control for the primary superchargerincluding a pressure-responsive element having pressure communicationwith said intake manifold and means coacting with said element operatingto automatically regulate the degree of charging pressure applied tosaid manifold, a variable datum control for said turbo-superchargerincluding a pressure-responsive element having pressure communicationwith a source functioning as a refer-- ence with respect to carburetorinlet pressure and means coacting with said latter element operating toautomatically regulate the degree of exhaust pressure utilized indriving said turbine, a device adjustable to vary the speed of theengine independently of the throttle, and means having-a commonoperative connection with said variable datum controls and said devicewhereby said controls and device may be set to maintain a predeterminedschedule of manifold pressure, carburetor inlet pressure and engine R.P. M.

4. Control mechanism for an aircraft engine having a throttle-controlledinduction passage provided with a carburetor inlet located anterior thethrottle and a supercharging system including a primary supercharger andan auxiliary turbo supercharger V in series therewith and powered by anexhaust-driven turbine; said means coacting therewith operating toautomati- 7 cally regulate the degree of exhaust pressure utilized indriving said turbine, a device adjustable to vary engine speed, apilot's control lever, means controllable by said lever having anoperative connection with said variable datum control means and saiddevice whereby the control means and device may be set within a certainrange of movement of the lever to automatically maintain a predeterminedschedule of manifold pressure, carburetor inlet pressure and engine R.P. M. and means whereby the automatic speed control may be overriddenand the engine speed controlled independentlyof said variable datumcontrol.

5. Control mechanism for an aircraft engine provided with a carburetorinlet located anterior the throttle, an intake manifold and asupercharging system including a primary supercharger and a secondarysupercharger arranged in series with the first-named supercharger; saidmechanism comprising a variable datum control for automaticallyregulating the charging Dressures of said superchargers including aspringloaded pressure-responsive element having pressure communicationwith said manifold and another spring-loaded pressure-responsive elementhaving pressure communication with a source representative of carburetorinlet pressures, a shaft, cams mounted on said shaft and coordinated tovariably load the springs of said elements and automatically provide apredetermined schedule of manifold pressure and carburetor inletpressure, a throttle lever. and means connecting the throttle lever withsaid shaft.

6. Control mechanism for an aircraft engine having a throttle inductionpassage provided with a carburetor inlet located anterior the throttle,an intake manifold and a supercharging system including a primarysupercharger and a secondary supercharger arranged in series therewith;said mechanism comprising a variable datum control including aspring-loaded pressure-responsive element having pressure communicationwith said intake manifold and operating to automatically regulate thedegree of charging pressure and another spring-loaded pressureresponsiveelement having pressure communication with a source representative ofcarburetor inlet pressures for'regulating the secondary supercharger, adevice adjustable to vary the speed of the engine independently of thethrottle, a shaft, cams mounted on said shaft and coordinated tovariably load the springs of said elements and regulate said device toautomatically maintain a predetermined schedule of manifold pressure,carburetor inlet pressure and engine R. P. M., a throttle lever, andmeans connecting the throttle lever with said shaft.

7. Control mechanism for an aircraft engine having a throttle controlledinduction passage provided with a carburetor inlet located anterior thethrottle, a supercharger driven in relation to the speed of the engineand a turbo supercharger arranged in series therewith and powered by anturbo supercharger arranged to discharge air unexhaust-driven turbine;said mechanism comprising a variable datum control including an elementresponsive to charging pressures for regulating the throttle to therebyregulate the degree of char ing pressure of the engine-drivensupercharger, another variable datum control for regulating the degreeof exhaust pressure utilized in driving the turbine including an elementresponsive to pressures having as a reference carburetor inletpressures, and means having an operative connection with the throttlefor simultaneously setting said control means in predeterminedcoordinated relation whereby a predeter mined schedule of intakemanifold pressure and carburetor inlet pressure is obtained for eachposition of the throttle.

8. Control mechanism for an aircraft engine having an exhaust conduit, athrottle-controlled induction pamage provided with a carburetor inletlocated anterior the throttle and a supercharging system including aprimary supercharger and an auxiliary turbo supercharger powered by anexhaust-driven turbine; said mechanism comprising a variable datumcontrol unit for said primary supercharger including apressure-responsive element having pressure communication with theinduction passage posterior to the primary supercharger and a datumspring for var iably loading said element, a blast gate for applyingexhaust pressure to driving the turbine, an exhaust datum control forsaid turbo supercharger including a pressure-responsive element inpressure communication with the induction passage anterior thecarburetor inlet and having an operative connection with said blast gateto regulate the degree of charging pressure applied to the inductionconduit anterior to the throttle and a spring for variably loading saidelement, a shaft, cams mounted on said shaft and having an operativeconnection with said springs for variably loading the latter, a throttlelever, and means connecting said throttle lever with said shaft.

9. Control mechanism for an aircraft engine having induction and exhaustconduits and a fuel-feeding system including a carburetor, saidinduction conduit including a carburetor air inlet portion and an intakemanifold portion, a supercharger arranged to discharge air underpressure into the intake manifold portion and der pressure into saidpassage anterior to the earburetor inlet portion and powered by anexhaustdriven turbine; said mechanism comprising means for regulatingthe exhaust pressure applied to driving the turbine, control means forsaid superchargers including an element responsive to pressures in saidmanifold portion and another element responsive to pressures prevailingin the region of the carburetor inlet, variable datum means manuallyregulable to give a predetermined simultaneous coordinated setting tosaid elements, and means operatively connecting said second-namedelement with said exhaust pressure regulating means for automaticallycontrolling the speed of the turbine.

10. Control mechanism for an aircraft engine having an induction passageprovided with a throttle-controlled carburetor air inlet portion and anintake manifold portion, a supercharger located to discharge into saidmanifold portion and another supercharger arranged to discharge .intosaid carburetor inlet portion; said control mechanism includingpressure-responsive means having pressure communication, respectively,with said intake manifold portion posterior to the said first-namedsupercharger and with said carburetor inlet portion anterior thethrottle and posterior to said second-named supercharger, and variabledatum means arranged to give a predetermined simuitaneous coordinatedsetting to said pressure-responsive means and coordinate the operationof said superchargers to maintain a predetermined schedule of carburetorinlet pressure and intake manifold pressure.

11. Control mechanism for an aircraft engine having an exhaust passageprovided with a blast gate, a throttle controlled induction passage anda supercharging system including a primary supercharger driven inrelation to the speed of the engine and an auxiliary turbo superchargerpowered by an, exhaust-driven turbine; said mechanism comprising avariable datum control for regulating the degree of charging pressure ofsaid primary supercharger including an element responsive to chargingpressures posterior to the throttle, another variable datum control forsaid turbo supercharger including a pressure-responsive element havingpressure communication with a, source representative of pressuresprevailing in said passages anterior the throttle, electric meansoperable to position the blast gate and thereby control the degree ofexhaust used in driving the turbine, a source of electric power such asa battery, an electric circuit connecting said source with said gatepositioning means, a switch interposed in said circuit and influenced bysaid second-named element to close the circuit to the gate positioningmeans when turbo supercharger pressure is required to maintain thepressure in said induction passage at a value determined by the fittingof said second-named variable datum con-- 12. In a control for an-internal combustion engine having an exhaust manifold and a throttlecontrolled induction conduit provided with a carburetor inlet portionanterior the throtthe and a multi-step supercharger system including amechanically-driven supercharger located posterior to the throttle and aturbo supercharger located anterior to the throttle and powered by anexhaust-driven turbine, said turbine having a driving rotor located toreceive exhaust gases from said exhaust manifold, an exhaust gate andelectrical means for variably position- 2!. ing said gate totherebyregulate the exhaust pressure applied to said rotor, variabledatum means for controlling the charging pressures of said superchargersincluding a pressure-responsive element having pressure communicationwith the induction conduit posterior to the throttle and anotherpressure-responsive element having pressure communication with saidconduit anterior to the carburetor inlet, a switch operatively connectedto one of said elements, and electrical means connecting said switchwith said blast gate positioning means.

' 13. In a control for an internal combustlon engine having an exhaustconduit and a supercharging system including a turbo superchargerpowered by a turbine provided with a driving rotor subjected to exhaustpressure, a blast gate associated with said exhaust conduit, an exhaustdatum control for said supercharger, electrical means for positioningthe blast gate to thereby control the degree of exhaust pressure used indriving the turbine, a source of electric power such as a battery, anelectric circuit connecting said source with said gate positioningmeans, a switch interposed in said circuit and influenced by saidexhaust datum control to close the circuit to the gate positioning meanswhen charg-- ing pressure drops below or exceeds a value determined bysaid control, and switch means in said circuit operating to maintain thespeed of the turbo within minimum and maximum lmits.

14. In a control for an aircraft engine having an induction conduit andan exhaust conduit,

a super-charging system including a turbo supercharger arranged todischarge into said induction conduit and powered by an exhaust-driventurbine provided with a rotor arranged to receive gases from saidexhaust conduit and a movable gate for said exhaust conduit; an electricmotor for variably positioning said gate to thereby regulate the exhaustpressure utilized in driving said rotor, variable datum means forcontrolling the charging pressure including a pressure-responsiveelement having pressure communication with a source representative ofpressures prevailin in said conduits, a contact switch controlled bysaid element, an electric circuit operatively connecting said switch tosaid motor, and another contact switch in said circuit responsive toturbine speed and arranged to break the circuit to said motor when theturbine attains a predetermined speed.

15. In a control for an aircraft engine having a throttle controlledintake passage and an exhaust manifold, a supercharging system includinga turbo supercharger powered by a turbine provided with a driving rotorarranged to receive gases from said exhaust manifold and a blast gatelocated in said exhaust manifold for regulating the pressure applied tosaid rotor; an .0

electric motor for variably positioning said gate, variable datumcontrol means for said supercharger, an electric circuit connecting saidcontrol means to said motor, another electric current and meansinterposed in said latter circuit 66 operating through said motor tomove the blast gate to a position effective to maintain the turbine in astate 01' rotation during idling and lowpower speeds of the engine.

16. In a control for an aircraft engine having 7 an intake passage andan exhaust conduit, a supercharging system including a primarysupercharger and an auxiliary turbo supercharger in series therewithpowered by a turbine having a driving rotor located to receive exhaustgases from said exhaust conduit and a movable blast gate coacting withsaid conduit: variable datum control means for said superchargers havingan operative connection with said blast gate for automaticallypositioning the latter to produce a turbo charging pressure inaccordance with the demands of the control, and means effective to movethe blast gate toward closed position independently of said controlmeans when the engine is throttled to idle and low-power speeds.

17. In a control for an aircraft engine having an intake passage and anexhaust conduit, a supercharging system for the engine including a turbosupercharger arranged tosupply pres-. sure to said engine and powered bya turbine having a driving rotor located to receive exhaust gases fromsaid exhaust conduit and a movable blast gate located in said conduit;means for variably positioning said gate to thereby control the exhaustpressure utilized in driving said rotor including variable datum controlmeans for said supercharger having an operative connection with saidgate positioning means, and meansresponsive to a function of the enginelimiting the closing position of said gate independently of sad controlmeans to thereby maintain the turblue in a state of rotation when thevariable datum control would otherwise permit the turbo to stall. 4

18. In a control for an aircraft engine having an induction passage andan exhaust conduit, a supercharging system including a turbosupercharger arranged to deliver air under pressure to said engine andpowered by a turbine having a driving rotor located to receive, exhaustgases from said conduit and means for controlling the exhaust applied tosaid rotor; a variable datum control including a pressure-responsiveelement having pressure communication with said passage and operativelyconnected to-said exhaust control means, and means responsive to afunction of the engine for maintaining the turbo supercharger at aminimum turbo boost during idling and low engine speeds independently ofsaid' variable datum control.

19. In a control for an aircraft engine having an induction passage andan exhaust conduit, a supercharging system including a turbosupercharger arranged to deliver pressure to said induction passage andpowered by a turbine having a driving rotor located to receive exhaustgases from said exhaust conduit and a movable blast gate for regulatingthe degree of exhaust pressure applied to said rotor; electrical meansfor positioning said gate, variable datum means for varying the degreeof charging pressure including a pressure-responsive element movable inrelation to pressures prevailing in saidpassage, a source of electricpower, an electrical circuit operatively connecting said source withsaid gate-positioning means, a. switch interposed in said circuit andcontrollable by said element to regulate the position of the gate inaccordance with charging pressure, and means for maintainin a minimumturbine speed during low and idling speeds of the engine including adevice having an element responsive to a differential in pressurebetween atmospheric and that prevailing in said passage and a switchcontrolled by said element adapted to close the circuit between thesource of power and gate-positioning means when the diiferential attainsa predetermined value.

7 20. In a control for an aircraft engine having regulating the speed ofthe turbine including a pressure-responsive element having pressurecommunication with a source representative of s the pressures prevailingin said passage, an electric circuit operatively connecting said elementwith said motor to variably position said gate in accordance withdemands of the engine, and means for maintaining a minimum turbo boostat times when the engine is at idling and low power speed including anexpansible bellows having pressure communication with the atmosphere andwith said passage and a switch interposed in said circuit and influencedby said bellows in a manner such that when the pressure in said passagedrops below atmospheric said circuit is closed and said motor drivenindependently of said exhaust datum control in a direction to move thegate toward closed position.

21. In a control for an aircraft engine having an intake passage and anexhaust conduit, a

supercharging systemincluding a turbo supercharger powered by a turbinehaving a driving rotor located to receive pressure from said exhaustconduit and a blast gate coacting with said conduit; variable datummeans for automatically controlling the exhaust utilized in driving theturbine, a motor for variably positioning said gate, an electric circuitoperatively connecting said variable datum means with said motor, amaximum speed switch in said circuit, a centrif ugal governorcontrolling said switch, said governor being operatively connected tosaid turbine and arranged to open said switch when the turbo attains apredetermined maximum speed.

22. In combination with an internal combustion engine having aninduction passage, a pair of superchargers in series relation in saidpassage, and means responsive to the diflerential in pressure across oneof said superchargers for controlling the operation of the other of saidsuperchargers.

23. In combination with an internal combustion engine having aninduction passage, a pair of superchargers in series relation in saidpassage, and means jointly responsive to the pressure rise across one ofsaid superchargers and to the pressure at the outlet of the other ofsaid superchargers for controlling the operation of one of saidsuperchargers.

24. In combination with an internal combus tion engine having aninduction passage including a carburetor, an exhaust gas drivensupercharger in said passage anterior to the carburetor, meansresponsive to the pressure at the carburetor inlet for controlling theoperation of said supercharger, and means responsive to pressuresvarying with variations in engine speed for modifying said control.

25. In combination with an internal combustion engine having aninduction passage, a supercharging system including a main blower and anauxiliary blower arranged to supply air .under pressure to the enginethrough said passage, means responsive to variations in chargingpressures for regulating the pressure rise across one of said blowers,and means responsive to variations in engine speed for regulating thepressure rise across the other of said blowers.

26. In combination with an internal combustion engine having aninduction passage, a supercharging system including a main blower and anauxiliary blower arranged to supply air under pressure to the enginethrough said passage, a variable datum control including means forregulating the pressure rise across the main blower to maintain apredetermined charging pressure. and means responsive to variations inpressure rise across the main blower for regulating the operation of theauxiliary blower.

27. In combination with an internal combustion engine having aninduction passage including an intake manifold, a supercharging systemincluding an engine-driven supercharger and a turbo superchargerarranged to supply air under pressure to the engine through said passageand powered by an exhaust-driven turbine, means for automaticallyregulating the pressure rise across the engine-driven supercharger tomaintain a schedule of manifold pressure, and means for varying thepressure rise across the turbo supercharger, said latter means beingresponsive to a function of the speed of the engine-driven supercharger.

28. In combination with an internal combustion engine having athrottle-controlled induction passage, a supercharging system includingan engine-driven supercharger and a turbo supercharger powered by anexhaust-driven turbine, power control means including means forautomatically positioning the throttle to maintain a predeterminedscheduled charging pressure, and means automatically operating as afunction of engine speed for regulating the speed of the turbosupercharger to maintain a pressure schedule anterior the throttle suchas will permit scheduled charging pressure with a minimum of throttleloss.

29. In combination with an internal combustion engine having athrottle-controlled induction passage including a carburetor inletanterior the throttle and an intake manifold posterior the throttle, andan exhaust conduit provided with a movable turbine blast gate; asupercharging system including an engine-driven supercharger providing afirst supercharging stage and a turbo supercharger constituting anauxiliary or second stage and powered by an exhaust-driven turbine,variable datum means functioning to variably position the throttle tomaintain scheduled manifold pressure, and means influenced by carburetorinlet pressure and the pressure rise across the engine-drivensupercharger having an operative connection with the blast gate wherebya schedule of carburetor inlet pressure is obtained such as willmaintain scheduled manifold pressure with a minimum of throttle loss.

30. In combination with an internal combustion engine having athrottle-controlled induction passage including a carburetor or inletanterior the throttle and an intake manifold posterior the throttle, andan exhaust conduit provided with a movable turbine blast gate; asupercharging system including an engine-driven supercharger providing afirst supercharging stage and an exhaust-driven turbo superchargerproviding an auxiliary or second stage, variable datum means functioningto variably position the throttle to maintain scheduled chargingpressure, means responsive to carburetor inlet pressure and acoordinated differential in pressures prevailing between the throttleand engine-driven supercharger and in the intakemanifold, and meansoperatively connecting said latter means to the blast gate to regulatethe speed of the turbo in accordance with scheduled manifold pressuresand carburetor inlet pressures.

31. In an airplane powered by an internal combustion engine having aninduction passage provided with a carburetor inlet and an exhaustconduit provided with a movable blast gate, a supercharging systemincluding an engine-driven primary supercharger and a secondary turbosupercharger in series therewith, said turbo supercharger being drivenby a turbine whose speed of rotation is governed by the position of theblast gate, and means for variably positioning said gate including meansresponsive to variations in carburetor inlet pressure and engine-drivensupercharger pressure. v

32. In an internal combustion engine having an intake passage providedwith a throttle and an exhaust system, a supercharger operativelyassociated with said intake passage and adapted to be driven by exhaustgas pressure from said exhaust system, a blast gate for controlling thepressure of the exhaust gases which operate said supercharger, andvariable-datum means for regulating the position of said gate includinga movable member having an operative connection with said gate andpressure-differential responsive means for actuating said member havinpressure communication with said passage anterior and posterior to thethrottle.

33. In an internal combustion engine having a throttle-controlled intakepassage with a 'carburetor inlet and an exhaust system, an engine'-driven supercharger operatively associated with said intake passageposterior the carburetor inlet and throttle, a turbo superchargeroperatively associated with said passage anterior the carburetor inletand adapted to be driven by exhaust gas pressure from said exhaustsystem, a blast gate for controlling the pressure of the exhaust gaseswhich operate the turbo supercharger, and variable datum means forregulating the position of said gate including a movable member havingan operative connection with the gate and pressure-differentialresponsive means for actuating said member utilizing operating pressureshaving as a reference source carburetor inlet pressure and thedifferential resulting from pressures between the throttle andenginedriven supercharger and posterior said latter supercharger.

34. In combination with an internal combustion engine having athrottle-controlled induction passage including a carburetor inletanterior the throttle and an intake manifold posterior the throttle, andan exhaust conduit provided with a movable turbine blast gate; asupercharging system including an engine-driven supercharger providing afirst supercharging stage and an exhaust-driven turbo superchargerproviding an auxiliary or second stage, a variabledatum power controlincluding an element responsive to manifold pressure for variablypositioning the throttle to maintain scheduled charging pressures andanother element responsive to carburetor inlet pressure and providedwith an operating member having an operative connection with the blastgate to maintain a schedule of carburetor inlet pressures, a deviceresponsive to pressure rise across theenginedriven superchargercoordinated with said latter element for Joint control of said operatingmember, and means for regulating the speed of the engine independentlyof said power control.

35. The combination of claim34, wherein said device consists of adiaphragm connected to said element and subjected on one side topressures prevailing between the throttle and enginedriven superchargerand on the opposite side to pressures prevailing in the intake manifold.

FRANK C. MOCK. JAY A. BOLT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,557,793 Berger et al. Oct. 20,1925 2,024,202 Berger Dec. 17, 1935 2,285,344 Marples et al. June 2,1942 2,297,235 Miiller Sept. 29, 1942 2,305,810 Miiller Dec. 22, 19422,336,844 Buck Dec. 14, 1943 2,355,759 Stokes Aug. 15, 1944 2,373,139Morris Apr. 10, 1945 2,376,142 Hoffman et a1. May 15, 1945 2,428,531Schom Oct. 7,1947

FOREIGN PATENTS Number Country Date 479,278 Great Britain Jan. 28, 1938684,902 France Mar. 24, 1930 I Certificate of Correction Patent No.2,480,758 August so, 1949 FRANK C. MOCK ET AL.

It is hereby certified that errors appear in the printed specificationof the above numbered patent requiring correction as follows:

Column 5, line 17, for otherwies read otherwise; line 58, for the wordsupercharge read supercharger; column 7, line 66, for relay R read relayR column 18, line 72, after throttle insert controlled; column 20, line23, after said, second occurrence, strike out oontrol line 26, after tostrike out the; column 21, line 31, for lmits read ltmtts; lines 64 and65, for current read circuit; column 22, line 26, for sad read sazd;column 24, llne 65, strike out or and that the said Letters Patentshould be read with these corrections therein that the same may conformto the record of the case in the Patent Oflice.

Signed and sealed this 21st day of February, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommisaioncr of Patcn'ta.

